Torpedo launch system

ABSTRACT

A submarine or other marine vessel has a payload launch system with an impulse tank ( 7 ) connected via a straight water inlet tube ( 20 ) to an inlet orifice ( 3 ) in an outer casing ( 1 ) of the vessel. A payload launch tube being a torpedo tube ( 8 ) extends through the impulse tank ( 7 ) to the outer wall ( 1 ), and also extends through a pressure hull ( 4 ) of the submarine to terminate at a rear door ( 9 ). The torpedo tube has an inlet valve ( 10 ) within the impulse tank ( 7 ). In order to provide pressurised water to the torpedo tube ( 8 ) to launch a torpedo ( 25 ), an impeller ( 19 ) is mounted in the impulse tank which pumps water into the impulse tank ( 7 ) to develop a pressure which is transmitted to the torpedo tube ( 8 ) when the valve ( 10 ) is opened. The impeller ( 19 ) is driven by an electric motor unit ( 21 ) which is connected to a power supply ( 22 ) by cables ( 30 ) which pass through the pressure hull ( 4 ). The impulse tank ( 7 ) and the motor unit ( 21 ) are between the outer casing ( 1 ) and the pressure hull ( 4 ) and the impulse tank ( 7 ) is preferably spaced from the pressure hull ( 4 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a payload launch system. It alsorelates to a marine vessel incorporating such a payload launch system.The payload may, for example, be a torpedo.

2. Summary of the Invention

Many conventional torpedo launching systems use a water-pressurisedimpulse tank to force a torpedo out of its tube. An increasingly commonmethod for launching torpedoes is the Air Turbine Pump (ATP) motivatedWeapon Discharge System (WDS).

The operation of a conventional ATP positive discharge torpedo launchsystem in a submarine is illustrated in FIG. 1 of the accompanyingdrawings.

FIG. 1 is a schematic representation of a conventional torpedo launchingsystem installed within the outer casing (1) and at the bow end of asubmarine.

The outer casing has an aperture in the bow which can be covered by abow shutter (2), and a water inlet orifice (3) aft of the bow. Apressure hull (4) lies within the outer casing, and encloses an innerchamber (5). The front bulkhead of the pressure hull and the outercasing of the submarine define an outer chamber (6). An impulse tank (7)is mounted fore of the pressure hull, in the outer chamber, and thefront bulkhead of the pressure hull comprises the aft wall of theimpulse tank. A torpedo tube (9), extends from the inner chamber (5),passing through the pressure hull and impulse tank and continues intothe outer chamber, ending close to the outer casing bow shutter. Thetorpedo tube comprises a rear door (9) located in the inner chamber,through which a torpedo may be loaded into the tube; an inlet valve (10)located within the impulse tank, which forms the outlet of the impulsetank and serves to enable the flow of water from the impulse tank intothe torpedo tube during firing; and an open end, closable with a bow cap(11), within the outer chamber, through which the torpedo will exit whendischarged. The torpedo tube is installed at an attitude such that whena torpedo is discharged it will pass from the open end of the tube (whenthe bow cap is open), through the aperture in the outer casing (when thebow shutter (2) is open).

A pressurised air container (12), a programmable firing valve (PFV)(13), a control loop (14) and an operating console (15) are mountedinside the pressure hull.

The operating console (15) is connected to the control loop (14) whichcontrols the PFV (13). The PFV regulates the air flow rate and pressureof air which is released from the pressurised air container (12).

High pressure air via the PFV drives an air turbine (16) mounted in theinner chamber. The air turbine is connected to a reduction gearbox (17).A drive shaft extends from the reduction gearbox through the pressurehull, hull integrity being maintained by a shaft-sealed hull penetration(18), exiting the front bulkhead at a point inside the impulse tank,where it connects to an impeller (19), also located within the impulsetank. A water inlet tube (20) connects the intake face of the impellerto the water inlet orifice (3) in the outer casing. The water inlet tubeextends from the intake face of the impeller, passing through the wallof the impulse tank, bends through ninety degrees and connects to thewater inlet orifice.

Note that in the known arrangement described above, the impulse tank ismounted on the pressure hull. Other arrangements are known in which itis spaced therefrom.

This air driven discharge system uses high-pressure air to drive the airturbine which in turn drives the impeller.

The impulse tank (7) acts as a manifold around one or more, usuallyseveral, torpedo tubes.

A firing sequence may begin with the bow cap, bow shutter and rear doorbeing shut, and the torpedo tube drained. The rear door is then opened,the torpedo loaded and mechanically secured in the tube and the reardoor closed. The tube is flooded and equalised with the fluid pressureoutside the outer casing. The bow cap and bow shutter may then be openedand the torpedo released from the mechanical restraint. The inlet valveto the tube is opened and a PFV profile selected. High pressure air viathe PFV drives the air turbine, which in turn drives the impeller topressurise the impulse tank, thereby developing water pressure withinthe impulse tank which is transmitted to the inside of the torpedo tubevia the inlet valve. This water pressure forces the torpedo from itstube. The action of the impeller also has the effect of drawingadditional water (“follow-up water”) into the impulse tank via the waterinlet tube.

Regulation of the air flow rate and pressure of air delivered to the airturbine provides control over the torpedo's discharge parameters.

Despite their widespread use and established efficacy, ATP systems havea number of drawbacks.

The ATP system utilises high pressure air which is a secondary energysource within the submarine, hence requiring energy conversion in orderto provide additional supplies. Moreover, after firing, the air releasedrequires recompression.

Systems that rely on pneumatics and hydraulics have an additionalmaintenance burden leading to higher through life costs.

Systems that penetrate the pressure hull are often constrained withrespect to their orientation by the structural integrity requirements ofthe penetration. This can result in additional constraint(s) on thedischarge system, leading to a sub optimal solution for both thesubmarine and the discharge system.

SUMMARY OF THE INVENTION

It is therefore an aim of the present invention to address some of thedrawbacks associated with existing launching systems.

At its most general, the present invention proposes that the impellerwhich forces sea water into the impulse tank, and which provides theover pressure which launches the payload, is driven by an electric motorand the impulse tank and the motor are between the inner and outer hullof the vessel.

Thus, the present invention may provide a marine vessel having a payloadlaunch system, the vessel having an outer casing and an inner hull, thepayload launch system having at least one payload launch tube, animpulse tank for fluid, the impulse tank having an inlet for entry offluid into the impulse tank and an outlet communicating with the torpedotube, and an impeller inside the impulse tank for pressurising fluid inthe impulse tank so as to deliver pressurised fluid to the tube via theoutlet of the impulse tank to launch a payload from the tube;

-   -   wherein:    -   an electric motor unit is connected to the impeller to drive the        impeller, with the impulse tank and the motor being between the        inner hall and the casing.

By using an electric motor, the need for air compression, stowage andregulation is removed, increasing system efficiency and probablyreducing the mass of the equipment and the volume within the pressurehull.

It should be noted that the action of the impeller in deliveringpressurised fluid to the payload launch tube also normally has theeffect of drawing additional fluid (“follow-up water”) into the impulsetank via the inlet to the tank. Thus, the impulse tank is always full offluid, maintaining a positive pressure behind the weapon throughout thelaunch.

It is possible for the electric motor to be located in the impulse tankitself, as this has the advantage that the orientation of the impellerwithin the tank is not constrained by the geometry of the pressure hullof the submarine. Of course, the electric motor needs a power supply,and that power supply will normally be located within the pressure hull,and indeed may be the normal electrical power supply of the submarine.However, since the motor is an electric one, only the appropriate cablesneed extend through the pressure hull from the power supply to themotor, and it is a relatively straight forward matter for appropriatestatic pressure seals to be provided. Thus, the present inventionimproves the integrity of the pressure hull.

Moreover, because the orientation of the impeller is not dependent onpenetration of the pressure hull, it can be located so that its inletfaces directly the adjacent outer wall of the submarine. This permits ashorter water inlet tube from the outside of the submarine to theimpeller tank to be used, and also means that the tube need not bendthrough e.g. 90° as in the arrangement of FIG. 1 previously described.The impeller then faces directly the water inlet orifice of thesubmarine. A further advantage of this arrangement is that, since themotor is immersed, it will be cooled by the fluid (normally water) inthat tank.

However, it is not essential that the motor is in the impulse tank. Itmay be preferable for the motor to be located outside the impulse tank,but above it. Such a location has the advantage that it is then easy toaccess the motor, e.g. for maintenance and installation or removal. Moreparticularly, when the submarine is at the surface, the space betweenthe outer casing and the pressure hull is partially flooded, but with anair space above it. If the motor is then located in that air space, whenthe submarine floats, the motor is accessible for maintenance withoutthe submarine having to be in dry dock. Of course, when the submarine isunder water the air space is no longer present, and therefore the motorwill be immersed, and therefore cooled as previously described.

With such an arrangement it is still possible for the appropriate cablesto power the motor to extend through the pressure hull.

As has previously been mentioned with reference to FIG. 1, a submarinenormally has an outer casing and a pressure hull within that outercasing. The torpedo tube normally extends through the impulse tank andthe pressure hull to permit access to the torpedo tube from the interiorof the pressure hull. The outlet from the impulse tank is normallyformed by an inlet valve to the torpedo tube, so that the opening ofthat valve creates the outlet of the impulse tank.

In some conventional arrangements, such as the one illustrated in FIG.1, and within the present invention, it is usual for the impulse tank tobe mounted on an outer surface of the pressure hull. However, in thepresent invention, this is not necessary. As has been previouslymentioned, only the power cables to the motor need pass through thepressure hull, and the motor may be mounted outside the pressure hull.As has been previously mentioned the motor may be inside the impulsetank, or at other locations between the outer casing and the pressurehull. However, in any such case, it is not necessary that the impulsetank be mounted on the outside of the pressure hull. It could be spacedtherefrom. This latter arrangement has the advantage that theoverpressure generated within the impulse tank during the launch of thetorpedo is not transmitted directly to the pressure hull.

In the present invention, the impeller is preferably a centrifugalimpeller, as in the known arrangements, and the electric motor is a hightorque electric motor. Depending on the duty required of the system,there may or may not be a reduction gearbox between the motor and theimpeller.

While the invention has been discussed above primarily in relation to atorpedo launch system, the present invention provides a submarine havingsuch a torpedo launch system. In addition, the torpedo launch system inthe present invention is not limited to use on submarines, and may beused on other marine vessels. Also, although it will be normal for thefluid used in the torpedo launch system of the present invention to besea water, it is possible for other liquids to be used. Additionally thesystem may be scaled as appropriate to launch different payloads.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described below, by way of exampleonly, with respect to the accompanying drawings, in which:

FIG. 1 shows the layout of a conventional ATP Torpedo Launching System,and has already been discussed;

FIG. 2 shows the layout of an electrically driven Torpedo LaunchingSystem, being a first embodiment of the present invention; and

FIG. 3 shows the layout of an electrically driven torpedo launchingsystem, being a second embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 has already been discussed in relation to existing torpedolaunching systems. FIG. 2, which represents a final embodiment of thepresent invention, retains the numbering system of FIG. 1. In theembodiments described herein the arrangement of the outer casing,pressure hull and torpedo tube remains unchanged from existing systems,and will not be described again. The same reference numerals are used toindicate corresponding parts.

In the final embodiment of the present invention a high torque electricmotor unit (21) replaces the air turbine (16) present in existing ATPsystems, and is similarly connected to a reduction gearbox and animpeller. The pressurised air container, programmable firing valve andcontrol loop of existing torpedo launch systems are not present in thisembodiment. The electric motor unit is powered from the submarine's mainelectrical supply (22). A motor controller (23), located in the innerchamber, regulates the current/voltage profile of the electrical supplyto the motor. An operating console (15), also located in the innerchamber, facilitates the operation of the electric motor unit bytransmitting electrical signals to the motor controller.

In the first embodiment of the present invention, the impulse tank (7)is installed within the outer chamber and is stood off from the pressurehull (4). The electric motor unit (21), a reduction gearbox (17) and animpeller (19) are mounted inside the outer chamber (6) and within theimpulse tank (7). In this embodiment, the electric motor, reductiongearbox and impeller are mounted at an attitude such that the intakeface of the impeller faces the water inlet orifice (3) in the outercasing of the submarine. Note that, by suitable selection of the speedof the motor unit (21) it may be possible to omit the reduction gearbox(17) and connect the impeller (19) directly to the motor unit (21). Themotor controller (23) communicates electrically with the electric motorunit via power and sensor cables (30), which pass from the motorcontroller through the front bulkhead of the pressure hull in a cablegland (24) and continue through the aft wall of the impulse tank, intothe interior of the impulse tank where they are connected to theelectric motor unit. A straight water inlet tube (20) joins the intakeface of the impeller tank to the water inlet orifice (3).

The torpedo launching system of this embodiment, represented in FIG. 2,is ready to fire when a torpedo or other weapon (25) is loaded in thetorpedo tube (8), the rear door (9) is closed, and the inlet valve (10),bow cap (11) and bow shutter (2) are open. In this state the tube isflooded, with the torpedo mechanically restrained. Upon receipt of afiring signal from the torpedo operating console (15), the motorcontroller (23) activates a current/voltage profile which is derivedfrom the main electrical supply (22). The electrical current passesthrough the cable gland (24) and powers the electric motor unit (21),which in turn drives the impeller (19). The impeller rapidly pressurisesthe water in the impulse tank (7), this pressure surge passing via theinlet valve to the torpedo tube. The torpedo is released from themechanical restraint and is forced out of the tube. Water expelled fromthe impulse tank during this pressure surge is replaced with water drawnfrom the water inlet tube (20) by the impeller. Once the weapon hascleared the submarine's outer casing (1) it is free to navigate underits own power.

FIG. 3 illustrates a second embodiment of the present invention, againbeing a torpedo launching system. The embodiment of FIG. 3 is generallysimilar to that of FIG. 2, and again reference numerals used to indicatecorresponding parts.

However, in the embodiment of FIG. 3, the motor unit 21 is not in theimpulse tank 7. Instead, it is mounted above it. The motor unit 21 isstill between the pressure hull 4 and the outer casing 1 of thesubmarine, and the cables 30 again pass through a gland 24 to reach thepower supply 22 for the motor. Moreover, in this arrangement, since themotor 21 is above the impulse tank 7, it is convenient if the impeller19 is at the top of the impulse tank 17, adjacent the motor 21, andtherefore the torpedo tube 8 extends through the impulse tank 7 near thebottom thereof.

The positioning of the motor unit 21 above the impulse tank 7 has theadvantage that the motor unit 21 is readily accessible for maintenance,installation or removal. Moreover, when the submarine floats, althoughthe space between the casing 1 and the pressure hull contains water thesurface 26 of the water in which the submarine is floating fills thatspace only part-way up the casing 1, so that there is an air space 27above that surface 26. Since the motor unit 21 is located in that airspace 27, it can be accessed above the surface of the water. Thus, themotor unit 21 is accessible for maintenance with the submarine floating,rather than in dry dock. This is an advantage compared with thearrangement of FIG. 2, where it would probably be necessary for thesubmarine to be in dry dock for maintenance of the motor unit 21.

It should be noted that when the submarine is submersed, there is nolonger and air space 27 and the motor 21 is submerged in water. Thismeans that it will be cooled during operation.

FIG. 3 illustrates another variation from the embodiment of FIG. 2, inthat the water inlet tube does not extend to an inlet orifice in thecasing 1, but instead to an orifice 28 leading to a bow shutter volume31 within the casing 1. The bow shutter volume 31 is within the casing,but is flooded with water and thus water can be pumped from that space31 via the inlet tube 20 to the impeller 19.

Other features of this embodiment are similar to the second embodimentof the FIG. 2, and therefore will not be described in detail. However,it should be noted that FIG. 3 shows an arrangement in which the valveshutter 2 is displaced from the outlet of the torpedo tube 8.

The embodiments of the present invention discussed above illustrate atorpedo launching system in a submarine. However, the present inventionis not limited to this and the launching system may be used on othermarine vessels. Moreover, payloads other than torpedoes may be launchedby embodiments of the present invention.

1. A marine vessel having a payload launch system, the vessel having anouter casing and an inner hull, the payload launch system having atleast one payload launch tube, an impulse tank for fluid, the impulsetank having an inlet for entry of fluid into the impulse tank and anoutlet communicating with the launch tube, and an impeller inside theimpulse tank for pressurizing fluid in the impulse tank so as to deliverpressurized fluid to the launch tube via the outlet of the impulse tankto launch a payload from the launch tube; characterized in that: anelectric motor unit is connected to the impeller to drive the impeller,with the impulse tank and the motor being between the inner hull and thecasing.
 2. A marine vessel according to claim 1, wherein the impulsetank of the launching system is within the outer casing but spaced fromthe pressure hull.
 3. A marine vessel according to claim 1, wherein apower supply for said motor unit is located within the pressure hull andis connected to the motor unit by cables passing through the pressurehull.
 4. A marine vessel according to claim 1, wherein the launch tubeextends through the impulse tank and through the pressure hull.
 5. Amarine vessel according to claim 1, wherein the launch tube extends intothe impulse tank, the outlet of the impulse tank being in a wall of thelaunch tube within the impulse tank.
 6. A marine vessel according toclaim 1, wherein the motor unit is in the impulse tank.
 7. A marinevessel according to claim 1, wherein the motor unit is above the impulsetank.
 8. A marine vessel according to claim 1, wherein the impeller is acentrifugal impeller.
 9. A marine vessel according to claim 1, whereinthe motor unit is a high torque motor
 10. A marine vessel according toclaim 1, being a submarine.